nios2: define syscall_get_arch()

nios2: define syscall_get_arch()

syscall_get_arch() is required to be implemented on all architectures
in addition to already implemented syscall_get_nr(),
syscall_get_arguments(), syscall_get_error(), and
syscall_get_return_value() functions in order to extend the generic
ptrace API with PTRACE_GET_SYSCALL_INFO request.

Acked-by: Paul Moore <paul@paul-moore.com>
Acked-by: Ley Foon Tan <ley.foon.tan@intel.com>
Cc: Elvira Khabirova <lineprinter@altlinux.org>
Cc: Eugene Syromyatnikov <esyr@redhat.com>
Cc: Ley Foon Tan <lftan@altera.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: nios2-dev@lists.rocketboards.org
Cc: linux-audit@redhat.com
Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>
Signed-off-by: Paul Moore <paul@paul-moore.com>